A fuel cell system (hereinafter referred to as a fuel cell), which has a high conversion efficiency in electrochemically converting the chemical energy owned by the liquid fuel into electrical energy, attracts attention as effective energy supplying means (i.e., power generation method and device) from the viewpoint of energy saving and environmental protection. Furthermore, such a fuel cell system, which can continuously generate an electric power while the liquid fuel continues to be supplied, attracts attention as a power source for use in portable information equipment such as laptop personal computers of which the power consumption keeps increasing in accordance with functional advancement and as a transportable power source. Moreover, the fuel cell system can operate to drive equipment of larger power consumption and for a longer time than the conventional rechargeable battery.
Various problems must be solved in order to apply a power supply system of high energy efficiency, such as the fuel cell, to portable or transportable power sources as a substitute for the rechargeable battery by reducing the size and the weight of the system in the future.
Particularly, in a direct type methanol fuel cell (DMFC (Direct Methanol Fuel Cell)) that uses methanol as the liquid fuel and generates an electric power by taking protons out of the methanol, it is considered that the methanol, which is a deleterious substance, exerts large influences on not only the user but also the surrounding environment. Therefore, it is necessary to suppress the emission of the liquid fuel supplied to the fuel cell, intermediate products of chemical reactions and emission matters (products) from the fuel cell into the atmosphere as much as possible.
It is well known that methanol, which is inflammable and toxic, requires sufficient care in the storage and handling thereof. If the methanol leaked from the fuel cell adheres to the human body or is taken into the body by mistake, it is possible that the human body will be harmed.
Moreover, the liquid fuel is supplied by providing the fuel cell with a cartridge typed container that holds the liquid fuel, and the continuous supply of the liquid fuel is achieved by replacing the cartridge. However, if the cartridge that is supplying the liquid fuel in the fuel cell suddenly falls off the equipment, there is concern that a large amount of methanol might leak from a connection port, and the possibility of harming the human body is further increased.
Accordingly, in the fuel cell described in Japanese unexamined patent publication No. 2003-45468, a fuel storage section for storing a liquid fuel is provided in a fuel cartridge, and an absorber for absorbing the fuel is placed in a space between the fuel cartridge and the fuel storage section. If the fuel leaks from the fuel storage section when the used fuel cartridge is removed from the electronic equipment, the fuel is absorbed by the absorber placed in the space between the fuel storage section and the cartridge, preventing leakage of the fuel to the outside of the cartridge.
Moreover, in the fuel cell described in Japanese unexamined patent publication No. 2003-92128, the fuel cartridge is internally divided into two chambers by a partition, the divided first chamber serving as a chamber for storing the fuel and the second chamber serving as a chamber for storing emission matters from the fuel cell. The internal volumes of the two chambers are changed according to the fuel consumption by freely deforming the partition, and the emission matters are prevented from being emitted to the atmosphere by being stored.
However, the fuel cells described in JP 2003-45468 and JP 2003-92128 assume that the cartridge that holds the liquid fuel is not damaged or the liquid fuel does not leak from the connection port of the cartridge. There is no consideration for safety in the case where the cartridge is damaged by an impact, or the like, and the internal liquid fuel and the emission matters leak to the outside of the cartridge, at the worst, by informing the user of the leakage or other measures. Considering the popularization of portable information equipment employing the fuel cell in the future, various use methods are supposed. Therefore, in consideration of the leakage of the liquid fuel, a means for confirming the leakage by the user easily in the early stage is needed.
Particularly, in the case of DMFC, methanol (or a methanol aqueous solution) used for the fuel is colorless, and the liquid fuel is inconspicuous even when it leaks from the cartridge that holds the liquid fuel. Therefore, it is possible that the discovery of the leakage might be late. Moreover, when the fuel cell is employed as a power source for portable information equipment, the leakage of the liquid fuel to the outside might cause troubles of a short circuit in the main body or the peripherals of the equipment equipped with the fuel cell and the deterioration, contact failure and so on of electrical components. Furthermore, when methanol of a high concentration is used as a fuel as a consequence of an improvement in the fuel cell performance, the detection of fuel leakage becomes important in terms of safety.